Food labels should show how much exercise is needed to burn off the calories consumed, an expert has said.

For example, the calories in a can of fizzy drink take a person of average age and weight about 26 minutes to walk off.

Shirley Cramer, chief executive of the Royal Society for Public Health (RSPH) said that labelling should “also help people to change behaviour”,  and that there was “little evidence” that traffic light labelling actually changes behaviour.

In a personal view, published in The BMJ, Cramer said food and drinks should be labelled with “activity equivalent” calorie information. But the view, which has made headline news today, was first published by RSPH in January.

In the interview she pointed to research which found that 44% of people said current front-of-pack information was confusing.